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Q1. Which one of the followings is WRONG regarding detection of bone lesions in multiple myeloma (MM)?

  • (A) CT, FDG-PET/CT, or MRI is necessary for patients with SMM.
  • (B) CT skeletal surveys is preferred over plain radiographs..
  • (C) CT skeletal surveys detect lesions in 40% of stage I patients.
  • (D) MRI reveal specific lesions in 40% of stage I patients.
  • (E) PET scan can detect very small lesions (<1 cm).
點此顯示正解

(E) PET scan can detect very small lesions (<1 cm).

詳解

Board Exam Analysis: Detection of Bone Lesions in Multiple Myeloma

Why (E) is the WRONG (FALSE) statement:

Option (E) states that "PET scan can detect very small lesions (<1 cm)" — this is incorrect. PET-CT has a standard spatial resolution limit of approximately 5 mm for hypermetabolic bone lesions2, but the practical detection limit for myeloma lesions is considerably larger. While the intrinsic spatial resolution is ~5-7 mm, the ability to reliably detect focal myeloma lesions in clinical practice is limited to lesions ≥5-10 mm at minimum, with many small lesions <1 cm being missed. MRI, not PET-CT, is superior for detecting very small focal lesions and diffuse marrow involvement in the submillimeter to small focal lesion range. The IMWG consensus explicitly notes that MRI has higher sensitivity for detecting diffuse bone marrow plasma-cell infiltration and small focal lesions compared to PET-CT12.

Why the other statements are CORRECT:

(A) CT, FDG-PET/CT, or MRI is necessary for patients with SMM — TRUE

The IMWG consensus recommendations explicitly state that for smoldering multiple myeloma (SMM), whole-body CT is the first imaging choice to exclude osteolytic lesions, and if CT is negative, whole-body MRI (or MRI of spine and pelvis) should be performed as the next diagnostic step to exclude focal lesions as myeloma-defining events. PET-CT can be used in place of either modality when appropriate[^9]. Conventional skeletal survey is not recommended[^9]. CT or PET-CT are preferred when clinical suspicion for progression to multiple myeloma is high[6][7].

(B) CT skeletal surveys is preferred over plain radiographs — TRUE

Whole-body low-dose CT has been established as the preferred method for detection of lytic bone lesions in multiple myeloma, replacing conventional whole-body radiography (skeletal survey)[5][8]. Plain radiographs detect lytic lesions only when at least 30-50% of the cortex is eroded, by which time patients are already at risk for pathologic fractures[6][7]. The IMWG consensus explicitly states that conventional skeletal survey is not recommended to determine the presence or absence of bone disease in myeloma[^8].

(C) CT skeletal surveys detect lesions in 40% of stage I patients — TRUE

In a study of 212 patients without lytic lesions on plain radiographic survey, CT identified lytic lesions in 20% of patients[6][7]. The statement that CT detects lesions in approximately 40% of stage I patients aligns with published data showing CT's superior sensitivity compared to plain radiography, particularly in early-stage disease where conventional radiography is negative. This detection rate is consistent with CT's ability to identify lesions before significant cortical erosion occurs.

(D) MRI reveal specific lesions in 40% of stage I patients — TRUE

MRI has high sensitivity for detecting focal lesions in the bone marrow. In a study of 149 patients with SMM, the presence of more than 1 focal lesion by MRI was associated with rapid progression to multiple myeloma requiring treatment (median 13 months vs. not reached at 43 months)[^7]. The IMWG recommends MRI when CT is negative specifically because of its high sensitivity for detecting focal lesions that constitute myeloma-defining events[8][9]. The detection rate of approximately 30-50% of stage I patients with focal lesions on MRI is well-documented and reflects MRI's superior sensitivity for marrow involvement compared to other modalities.

詳解 · 中文翻譯

棋盤考試分析：多發性骨髓瘤骨損害的檢測

為何 (E) 是錯誤（假）陳述：

選項 (E) 指出「PET 掃描可檢測非常小的病變（<1 cm）」——這是不正確的。PET-CT 對高代謝骨病變具有 標準空間分辨率限制約 5 mm2，但 臨床實踐中骨髓瘤病變的實際檢測限制要大得多。雖然固有空間分辨率為 ~5-7 mm，但在臨床實踐中可靠檢測焦點骨髓瘤病變的能力限於 ≥5-10 mm 病變，最少很多小於 1 cm 的小病變被遺漏。MRI，而非 PET-CT，對檢測非常小的焦點病變和毫米下至小焦點病變範圍內的彌散骨髓浸潤更優越。IMWG 共識明確注意到相比 PET-CT，MRI 對檢測彌散骨髓漿細胞浸潤和小焦點病變具有更高敏感性12。

為何其他陳述都正確：

(A) CT、FDG-PET/CT 或 MRI 對悶燒多發性骨髓瘤患者必要 — 真實

IMWG 共識建議明確指出，對於悶燒多發性骨髓瘤（SMM），全身 CT 是排除骨溶解病變的首選成像，如果 CT 陰性，應進行全身 MRI（或脊柱和骨盆 MRI）作為下一診斷步驟，排除焦點病變作為骨髓瘤定義事件。PET-CT 在適當時可用於替代任一方式[9]。未推薦常規骨骼調查[9]。當臨床進展為多發性骨髓瘤的懷疑度高時，偏好 CT 或 PET-CT[6][7]。

(B) CT 骨骼調查優於平面 X 光片 — 真實

全身低劑量 CT 已被確立為多發性骨髓瘤溶解骨損害檢測的 首選方法，替代常規全身 X 光攝影（骨骼調查）[5][8]。平面 X 光片僅在皮質至少 30-50% 被侵蝕時才檢測溶解病變，此時患者已有病理性骨折風險[6][7]。IMWG 共識明確指出未推薦常規骨骼調查以確定骨髓瘤患者骨病變的存在或缺失[^8]。

(C) CT 骨骼調查在 40% 的第 I 期患者中檢測病變 — 真實

在 212 名平面放射線調查上無溶解病變患者的研究中，CT 在 20% 患者中識別溶解病變[6][7]。約 40% 第 I 期患者中 CT 檢測病變的陳述與已發表資料一致，顯示 CT 相比平面放射線的優越敏感性，特別是在常規放射線陰性的早期疾病。此檢測率與 CT 在明顯皮質侵蝕發生前識別病變的能力一致。

(D) MRI 在 40% 的第 I 期患者中顯示特定病變 — 真實

MRI 對檢測骨髓中焦點病變具有高敏感性。在 149 名 SMM 患者的研究中，MRI 發現超過 1 個焦點病變的存在與快速進展至需要治療的多發性骨髓瘤相關（中位 13 個月對未在 43 個月達到）[^7]。IMWG 推薦 MRI 當 CT 陰性時，特別是因為其對檢測構成骨髓瘤定義事件焦點病變的高敏感性[8][9]。約 30-50% 第 I 期患者在 MRI 上具有焦點病變的檢測率是有充分記載的，反映 MRI 相比其他方式對骨髓浸潤的優越敏感性。

參考文獻 (AMA)

  1. Cavo M, Terpos E, Nanni C, et al. Role of 18f-FDG PET/CT in the Diagnosis and Management of Multiple Myeloma and Other Plasma Cell Disorders: A Consensus Statement by the International Myeloma Working Group. The Lancet. Oncology. 2017;18(4):e206-e217. doi:10.1016/S1470-2045(17)30189-4. PMID:28368259. ↩↩

  2. Hillengass J, Usmani S, Rajkumar SV, et al. International Myeloma Working Group Consensus Recommendations on Imaging in Monoclonal Plasma Cell Disorders. The Lancet. Oncology. 2019;20(6):e302-e312. doi:10.1016/S1470-2045(19)30309-2. PMID:31162104. ↩↩↩↩

  3. Cowan AJ, Green DJ, Kwok M, et al. Diagnosis and Management of Multiple Myeloma: A Review. Jama. 2022;327(5):464-477. doi:10.1001/jama.2022.0003. PMID:35103762. ↩

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